Polar code retransmission method and apparatus

ABSTRACT

Embodiments of this application provide a polar code retransmission method and apparatus, to reduce retransmission complexity and improve transmission performance. The method includes: determining a first polar channel sequence including N polar channels and reliability of each of the N polar channels; determining, based on a coding parameter for an mth data transmission, a quantity Km of information bits that need to be transmitted during the mth data transmission, where the coding parameter includes at least one of the quantity of information bits and a code rate; determining Km polar channels with highest reliability in the first polar channel sequence; determining Km information bits based on locations, of information bits that need to be transmitted during first m−1 data transmissions, in the first polar channel sequence; and mapping the Km information bits to the Km polar channels for transmission.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/CN2017/095827 filed on Aug. 3, 2017, which claimspriority to Chinese Patent Application No. 201610819549.2, filed on Sep.12, 2016. The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and morespecifically, to a polar code retransmission method and apparatus.

BACKGROUND

In a communications system, usually data transmission reliability isimproved through channel encoding, to ensure communication quality. Apolar code (polar code) is an encoding manner that can achieve a Shannoncapacity and that has low encoding and decoding complexity. The polarcode is a linear block code. A generation matrix of the polar code isG_(N), and an encoding process of the polar code is x₁ ^(N)=u₁^(N)G_(N), where u₁ ^(N)=(u₁, u₂, . . . , u_(N)) is a binary row vector,G_(N)=B_(N)F₂ ^(⊗(log) ² ^((N))), a code length N=2^(n), and n≥0.

${F_{2} = \begin{bmatrix}1 & 0 \\1 & 1\end{bmatrix}},$and B_(N) is an N×N transposed matrix, such as a bit reversal matrix. F₂^(⊗(log) ² ^((N))) is a Kronecker power of F₂, and is defined asF^(⊗(log) ² ^((N)))=F⊗F^(⊗((log) ² ^((N))−1)).

In the encoding process of the polar code, some bits in u₁ ^(N) are usedto carry information and are referred to as information bits, and asequence number set of these information bits is denoted as A. The otherbits are set to fixed values that are agreed on by a transmit end and areceive end in advance and are referred to as fixed bits, and a sequencenumber set of these bits is represented by using a complementary setA^(c) of A. Without loss of generality, these fixed bits are usually setto 0. Actually, a fixed bit sequence may be randomly set provided thatthe transmit end and the receive end agree in advance. Therefore, anencoded bit sequence of the polar code may be obtained by using thefollowing method: x₁ ^(N)=u_(A)G_(N)(A), where u_(A) is an informationbit set in u₁ ^(N), and u_(A) is a row vector of a length K, in otherwords, |A|=K, |⋅| indicates a quantity of elements in the set, and Kindicates a quantity of elements in the set A and also indicates aquantity of to-be-encoded information bits; and G_(N)(A) is a submatrixthat is in the matrix G_(N) and that is obtained based on rowscorresponding to indexes in the set A, and G_(N)(A) is a K×N matrix.Selection of the set A determines performance of the polar code.

In communications application that is insensitive to a system latency, ahybrid automatic repeat request (HARQ) is a commonly used transmissionmethod for improving a system throughput. When transmitting aninformation block, a transmit device encodes the information block andsends the encoded information block to a channel. If a receive devicedecodes a received signal and finds that transmission succeeds, thereceive device sends an acknowledgement (ACK) message to the transmitdevice, so as to complete the transmission of the information block. Ifthe receive device decodes a received signal and finds that transmissionfails (for example, cyclic redundancy check fails), the receive devicetransmits a negative acknowledgement (NACK) message to the transmitdevice through a feedback link, and the transmit device retransmits theinformation block. Alternatively, when no ACK feedback sent by thereceive device is received within a specific period of time, thetransmit device also retransmits the information block. This processcontinues until the receive device correctly performs decoding. Toobtain a maximum link throughput, the receive device temporarily storesall received signals and decodes the received signals together with anewly received signal.

In an existing retransmission method, reliability of a polar channelneeds to be recalculated based on a current code rate during eachretransmission, and complexity is excessively high.

SUMMARY

In view of the above, embodiments of this application provide a polarcode (polar code) retransmission method, to reduce retransmissioncomplexity and improve transmission performance.

According to a first aspect, a polar code retransmission method isprovided, including: determining a first polar channel sequenceincluding N polar channels and reliability of each of the N polarchannels; determining, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate; determining K_(m) polar channels with highest reliabilityin the first polar channel sequence; determining K_(m) information bitsbased on locations, of information bits that need to be transmittedduring first m−1 data transmissions, in the first polar channelsequence; and mapping the K_(m) information bits to the K_(m) polarchannels for transmission, where m, K_(m), and N are positive integers,m is greater than 1, and K_(m) is less than N.

Specifically, a transmit device may determine the first polar channelsequence based on the reliability of each of the N polar channels, andadjust information bits based on the first polar channel sequence duringeach subsequent data transmission. In addition, before each datatransmission, the transmit device first needs to determine a codingparameter for this data transmission. It should be understood that thecoding parameter may include at least one of the following parameters: acode length (which may also be referred to as a quantity of encodedbits), a quantity of information bits, and a code rate. Afterdetermining the coding parameter for this transmission, the transmitdevice determines, based on the coding parameter, a quantity K_(m) ofinformation bits that need to be transmitted, and then selectscorresponding K_(m) polar channels and K_(m) information bits to performmapping and transmission. In this embodiment of this application, whenperforming the m^(th) data transmission, the transmit device determinesK_(m) information bits used for the m^(th) data transmission, and mapsthe K_(m) information bits to K_(m) polar channels with highestreliability for encoding and transmission.

Therefore, according to the polar code retransmission method in thisembodiment of this application, the same polar channel sequence is usedduring each data transmission, and the determined K_(m) information bitsare directly mapped to the K_(m) polar channels with highest reliabilityin the polar channel sequence for transmission, without recalculatingthe reliability of the polar channels before each retransmission. Thiscan reduce retransmission complexity and improve transmissionperformance, thereby improving user experience.

It should be understood that the reliability of the polar channels maybe calculated through density evolution (DE) or Gaussian approximation(GA).

In a first possible implementation of the first aspect, m is 2, and theK_(m) information bits are information bits that occupy K_(m) polarchannels with lowest reliability in the first polar channel sequenceduring a first data transmission.

Specifically, during a retransmission, the transmit device may selectinformation bits transmitted on polar channels with lowest reliabilityduring the first data transmission, and select K_(m) information bitswith lowest reliability that are corresponding to the polar channels toperform the retransmission. In this way, a decoding success rate of areceive device can be increased, and a quantity of retransmissions ofthe transmit device can be reduced.

With reference to the foregoing possible implementation of the firstaspect, in a second possible implementation of the first aspect, a coderate of the first data transmission is R, and a code rate of the m^(th)data transmission is

$\frac{R}{m},$where R is greater than 0 and less than 1; and the determining K_(m)information bits based on locations, of information bits that need to betransmitted during first m−1 data transmissions, in the first polarchannel sequence includes: determining K_(m-1) polar channels,corresponding to information bits that need to be transmitted during an(m−1)^(th) data transmission, in the first polar channel sequence, whereK_(m-1) is less than N and greater than K_(m); determining

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels with lowest reliability from the K_(m-1) polar channels;and determining the K_(m) information bits from information bits on the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions.

Specifically, before performing the m^(th) data transmission, thetransmit device may first determine the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels, with lowest reliability corresponding to the informationbits that need to be transmitted during the (m−1)^(th) datatransmission, in the first polar channel sequence, and then select theK_(m) information bits from information bits mapped to the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions, toperform the m^(th) data transmission.

Therefore, information bits corresponding to most unreliable polarchannels during all previous data transmissions are comprehensivelyconsidered, and the information bits are mapped to K_(m) polar channelswith highest reliability for retransmission, so as to enhancereliability of these most unreliable information bits, and increase adecoding success rate.

With reference to the foregoing possible implementations of the firstaspect, in a third possible implementation of the first aspect, themapping the K_(m) information bits to the K_(m) polar channels fortransmission includes: sorting the K_(m) information bits in descendingorder of reliability of the polar channels corresponding to the K_(m)information bits that need to be transmitted during the first datatransmission; and mapping, for transmission, the sorted K_(m)information bits to the K_(m) polar channels ranked in descending orderof reliability.

Specifically, during each retransmission, the K_(m) information bits maybe mapped, in descending order of the reliability of the polar channelsoccupied by the K_(m) information bits during the first datatransmission, to the K_(m) polar channels ranked in descending order ofreliability.

With reference to the foregoing possible implementations of the firstaspect, in a fourth possible implementation of the first aspect, beforethe determining, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, the method furtherincludes: determining the coding parameter for the m^(th) datatransmission.

Specifically, the transmit device may determine the coding parameter forthe m^(th) data transmission in a plurality of manners. Specifically,the coding parameter may be agreed on by the transmit device and thereceive device in advance, or may be determined by the transmit devicebased on feedback information from the receive device before eachretransmission. This is not limited in this embodiment of thisapplication.

With reference to the foregoing possible implementations of the firstaspect, in a fifth possible implementation of the first aspect, thedetermining the coding parameter for the m^(th) data transmissionincludes: determining a preset coding parameter as the coding parameterfor the m^(th) data transmission.

In a specific implementation, a code rate of an initial transmission maybe R, a code rate of a second transmission is

$\frac{R}{2},$a code rate of a third transmission is

$\frac{R}{3},$. . . , and a code rate of the m^(th) transmission is

$\frac{R}{m}.$

With reference to the foregoing possible implementations of the firstaspect, in a sixth possible implementation of the first aspect, thedetermining the coding parameter for the m^(th) data transmissionincludes: receiving feedback information sent by a receive device forthe (m−1)^(th) data transmission; and determining the coding parameterfor the m^(th) data transmission based on the feedback information forthe (m−1)^(th) data transmission.

In this way, the transmit device can adjust, by using the feedbackinformation sent by the receive device, a coding parameter such as acode rate, a code length, or a quantity of information bits, so as toadaptively change a code rate during a retransmission.

With reference to the foregoing possible implementations of the firstaspect, in a seventh possible implementation of the first aspect, thefirst polar channel sequence is generated by sorting the N polarchannels based on the reliability of each of the N polar channels.

In this way, the transmit device does not need to determine areliability value of each of the N polar channels during eachtransmission, but only needs to obtain the first polar channel sequenceobtained after the N polar channels are sorted based on reliabilityvalues. This reduces complexity and improves coding efficiency.

With reference to the foregoing possible implementations of the firstaspect, in an eighth possible implementation of the first aspect, thereliability of each polar channel is a polarization weight of the polarchannel.

With reference to the foregoing possible implementations of the firstaspect, in a ninth possible implementation of the first aspect, beforethe determining a first polar channel sequence including N polarchannels and reliability of each of the N polar channels, the methodfurther includes: calculating the polarization weight of each of the Npolar channels.

With reference to the foregoing possible implementations of the firstaspect, in a tenth possible implementation of the first aspect, thecalculating the polarization weight of each of the N polar channelsincludes: obtaining a first polarization weight vector by calculatingthe polarization weights W_(i) of the N polar channels according to thefollowing formula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of the first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

According to a second aspect, a polar code retransmission method isprovided, including: determining a first polar channel sequenceincluding N polar channels and reliability of each of the N polarchannels; determining, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate; determining K_(m) polar channels with highest reliabilityin the first polar channel sequence; and decoding, on the K_(m) polarchannels, data transmitted during the m^(th) data transmission, where m,K_(m), and N are positive integers, m is greater than 1, and K_(m) isless than N.

Therefore, according to the polar code retransmission method in thisembodiment of this application, during each data transmission, K_(m)polar channels are directly determined by using the same polar channelsequence, and received data is directly decoded on the K_(m) polarchannels, without recalculating reliability of the polar channels beforeeach reception of data retransmitted by a transmit device. This canreduce decoding complexity and improve transmission performance, therebyimproving user experience.

In a first possible implementation of the second aspect, the first polarchannel sequence is generated by sorting the N polar channels based onthe reliability of each of the N polar channels.

With reference to the foregoing possible implementation of the secondaspect, in a second possible implementation of the second aspect, themethod further includes: sending feedback information to a transmitdevice, so that the transmit device determines the coding parameter forthe m^(th) data transmission based on the feedback information.

With reference to the foregoing possible implementations of the secondaspect, in a third possible implementation of the second aspect, thereliability of each polar channel is a polarization weight of the polarchannel.

With reference to the foregoing possible implementations of the secondaspect, in a fourth possible implementation of the second aspect, beforethe determining a first polar channel sequence including N polarchannels and reliability of each of the N polar channels, the methodfurther includes: calculating the polarization weight of each of the Npolar channels.

With reference to the foregoing possible implementations of the secondaspect, in a fifth possible implementation of the second aspect, thecalculating the polarization weight of each of the N polar channelsincludes: obtaining a first polarization weight vector by calculatingthe polarization weights W_(i) of the N polar channels according to thefollowing formula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

According to a third aspect, a polar code retransmission apparatus isprovided, configured to perform the method in any one of the firstaspect or the possible implementations of the first aspect.Specifically, the apparatus includes units configured to perform themethod in any one of the first aspect or the possible implementations ofthe first aspect.

According to a fourth aspect, a polar code retransmission apparatus isprovided, configured to perform the method in any one of the secondaspect or the possible implementations of the second aspect.Specifically, the apparatus includes units configured to perform themethod in any one of the second aspect or the possible implementationsof the second aspect.

According to a fifth aspect, a polar code retransmission apparatus isprovided. The apparatus includes a receiver, a transmitter, a memory, aprocessor, and a bus system. The receiver, the transmitter, the memory,and the processor are connected to each other by using the bus system.The memory is configured to store an instruction. The processor isconfigured to execute the instruction stored in the memory, to controlthe receiver to receive a signal and control the transmitter to send asignal. In addition, when the processor executes the instruction storedin the memory, the execution enables the processor to perform the methodin any one of the first aspect or the possible implementations of thefirst aspect.

According to a sixth aspect, a polar code retransmission apparatus isprovided. The apparatus includes a receiver, a transmitter, a memory, aprocessor, and a bus system. The receiver, the transmitter, the memory,and the processor are connected to each other by using the bus system.The memory is configured to store an instruction. The processor isconfigured to execute the instruction stored in the memory, to controlthe receiver to receive a signal and control the transmitter to send asignal. In addition, when the processor executes the instruction storedin the memory, the execution enables the processor to perform the methodin any one of the second aspect or the possible implementations of thesecond aspect.

According to a seventh aspect, a polar code retransmission system isprovided, where the system includes the apparatus in any one of thethird aspect or the possible implementations of the third aspect and theapparatus in any one of the fourth aspect or the possibleimplementations of the fourth aspect; or the system includes theapparatus in any one of the fifth aspect or the possible implementationsof the fifth aspect and the apparatus in any one of the sixth aspect orthe possible implementations of the sixth aspect.

According to an eighth aspect, a computer-readable medium is provided,and is configured to store a computer program, and the computer programincludes instructions used to perform the method in any one of the firstaspect or the possible implementations of the first aspect.

According to a ninth aspect, a computer-readable medium is provided, andis configured to store a computer program, and the computer programincludes instructions used to perform the method in any one of thesecond aspect or the possible implementations of the second aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an application scenario according to anembodiment of this application;

FIG. 2 is a schematic flowchart of a polar code retransmission methodaccording to an embodiment of this application;

FIG. 3 is a schematic flowchart of another polar code retransmissionmethod according to an embodiment of this application;

FIG. 4 is a schematic flowchart of another polar code retransmissionmethod according to an embodiment of this application;

FIG. 5 is a schematic flowchart of another polar code retransmissionmethod according to an embodiment of this application;

FIG. 6 is a schematic block diagram of a polar code retransmissionapparatus according to an embodiment of this application;

FIG. 7 is a schematic block diagram of another polar code retransmissionapparatus according to an embodiment of this application;

FIG. 8 is a schematic block diagram of another polar code retransmissionapparatus according to an embodiment of this application;

FIG. 9 is a schematic block diagram of another polar code retransmissionapparatus according to an embodiment of this application;

FIG. 10 is a schematic diagram of transmission performance of a polarcode retransmission method according to an embodiment of thisapplication; and

FIG. 11 is a schematic diagram of transmission performance of anotherpolar code retransmission method according to an embodiment of thisapplication.

DETAILED DESCRIPTION

The following describes the technical solutions in the embodiments ofthis application with reference to accompanying drawings of theembodiments of this application.

The embodiments of this application may be applied to variouscommunications systems. Therefore, the following descriptions are notlimited to a particular communications system. For example, thecommunications system may be a Global System for Mobile Communications(GSM), a Code Division Multiple Access (CDMA) system, a Wideband CodeDivision Multiple Access (WCDMA) system, a general packet radio service(GPRS) system, a Long Term Evolution (LTE) system, an LTE frequencydivision duplex (FDD) system, an LTE time division duplex (TDD) system,or a Universal Mobile Telecommunications System (UMTS). All informationor data encoded by a base station or a terminal in the foregoing systemby using a conventional turbo code and LDPC code can be encoded by usinga polar code in the embodiments.

The base station may be a device for communication with the terminal.For example, the base station may be a base transceiver station (BTS) ina GSM or CDMA system, or may be a NodeB (NB) in a WCDMA system, or maybe an evolved NodeB (eNB or eNodeB) in an LTE system. Alternatively, thebase station may be a relay node, an access point, an in-vehicle device,a wearable device, a network-side device in a future 5G network, or thelike.

The terminal may communicate with one or more core networks through aradio access network (RAN). The terminal may be user equipment (UE), anaccess terminal, a subscriber unit, a subscriber station, a mobilestation, a mobile console, a remote station, a remote terminal, a mobiledevice, a user terminal, a wireless communications device, a user agent,or a user apparatus. The access terminal may be a cellular phone, acordless phone, a Session Initiation Protocol (SIP) phone, a wirelesslocal loop (WLL) station, a personal digital assistant (PDA), a handhelddevice having a wireless communication function, a computing device,another processing device connected to a wireless modem, an in-vehicledevice, a wearable device, a terminal in a future 5G network, or thelike.

FIG. 1 shows a wireless communications system 100 according to theembodiments of this specification. The system 100 includes a basestation 102, and the base station 102 may include a plurality of antennagroups. For example, one antenna group may include an antenna 104 and anantenna 106, another antenna group may include an antenna 108 and anantenna 110, and an additional group may include an antenna 112 and anantenna 114. Two antennas are shown for each antenna group; however,each group may have more or fewer antennas. The base station 102 mayadditionally include a transmitter chain and a receiver chain. A personof ordinary skill in the art may understand that the transmitter chainand the receiver chain each may include a plurality of components, suchas a processor, a modulator, a multiplexer, a demodulator, ademultiplexer, or an antenna related to signal transmission andreception.

The base station 102 may communicate with one or more access terminals,such as an access terminal 116 and an access terminal 122. However, itmay be understood that the base station 102 may communicate with almostany quantity of access terminals similar to the access terminal 116 andthe access terminal 122. The access terminal 116 and the access terminal122 may be, for example, cellular phones, smartphones, portablecomputers, handheld communications devices, handheld computing devices,satellite radio apparatuses, devices related to the Global PositioningSystems, PDAs, and/or any other appropriate devices used forcommunication in the wireless communications system 100. As shown in thefigure, the access terminal 116 communicates with the antenna 112 andthe antenna 114. The antenna 112 and the antenna 114 send information tothe access terminal 116 through a forward link 118, and receiveinformation from the access terminal 116 through a reverse link 120. Inaddition, the access terminal 122 communicates with the antenna 104 andthe antenna 106. The antenna 104 and the antenna 106 send information tothe access terminal 122 through a forward link 124, and receiveinformation from the access terminal 122 through a reverse link 126. Ina frequency division duplex (FDD) system, for example, the forward link118 may use a frequency band different from that used by the reverselink 120, and the forward link 124 may use a frequency band differentfrom that used by the reverse link 126. In addition, in a time divisionduplex (TDD) system, the forward link 118 and the reverse link 120 mayuse a same frequency band, and the forward link 124 and the reverse link126 may use a same frequency band.

Each antenna group or each area or both designed for communication arereferred to as sectors of the base station 102. For example, the antennagroup may be designed to communicate with an access terminal in a sectorin a coverage area of the base station 102. During communication throughthe forward link 118 and the forward link 124, a transmit antenna of thebase station 102 may increase signal-to-noise ratios of the forward link118 for the access terminal 116 and the forward link 124 for the accessterminal 122 through beamforming. In addition, compared with a case inwhich a base station performs sending to all access terminals of thebase station by using a single antenna, when the base station 102performs, through beamforming, sending to the access terminal 116 andthe access terminal 122 that are randomly scattered in the relatedcoverage area, less interference is caused to a mobile device in aneighboring cell.

At a given time, the base station 102, the access terminal 116, and/orthe access terminal 122 may be wireless communications sendingapparatuses and/or wireless communications receiving apparatuses. Whensending data, a wireless communications sending apparatus may encode thedata for transmission. Specifically, the wireless communications sendingapparatus may have (for example, generate, obtain, or store in a memory)a specific quantity of information bits that need to be sent to thewireless communications receiving apparatus over a channel. Theinformation bits may be included in a transport block or a plurality oftransport blocks of data, and the transport block may be segmented togenerate a plurality of code blocks. In addition, the wirelesscommunications sending apparatus may encode each code block by using apolar encoder, so as to improve data transmission reliability, therebyensuring communication quality.

FIG. 2 is a schematic flowchart of a polar code retransmission method200 according to an embodiment of this application. The method 200 maybe applied to the wireless communications system 100 in FIG. 1. However,this embodiment of this application is not limited thereto. In addition,the method 200 may be performed by a network device, or may be userequipment. As shown in FIG. 2, the method 200 includes the followingsteps:

S210. Determine a first polar channel sequence including N polarchannels and reliability of each of the N polar channels.

S220. Determine, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate.

S230. Determine K_(m) polar channels with highest reliability in thefirst polar channel sequence.

S240. Determine K_(m) information bits based on locations, ofinformation bits that need to be transmitted during first m−1 datatransmissions, in the first polar channel sequence.

S250. Map the K_(m) information bits to the K_(m) polar channels fortransmission.

Herein, m, K_(m), and N are positive integers, m is greater than 1, andK_(m) is less than N.

Specifically, a transmit device may determine the first polar channelsequence based on the reliability of each of the N polar channels, andadjust information bits based on the first polar channel sequence duringeach subsequent data transmission. In addition, before each datatransmission, the transmit device first needs to determine a codingparameter for this data transmission. It should be understood that thecoding parameter may include at least one of the following parameters: acode length (which may also be referred to as a quantity of encodedbits), a quantity of information bits, and a code rate. Afterdetermining the coding parameter for this transmission, the transmitdevice determines, based on the coding parameter, a quantity K_(m) ofinformation bits that need to be transmitted, and then selectscorresponding K_(m) polar channels and K_(m) information bits to performmapping and transmission. In this embodiment of this application, whenperforming the m^(th) data transmission, the transmit device determinesK_(m) information bits used for the m^(th) data transmission, and mapsthe K_(m) information bits to K_(m) polar channels with highestreliability for encoding and transmission.

In this way, the K_(m) polar channels used for the m^(th) datatransmission are all selected based on the first polar channel sequence.To be specific, a polar channel sequence occupied by information bitsthat need to be transmitted during a second data transmission is asub-sequence of the first polar channel sequence, a polar channelsequence occupied by information bits that need to be transmitted duringa third data transmission is also a sub-sequence of the first polarchannel sequence, and so on. A polar channel sequence occupied byinformation bits that need to be transmitted during each subsequentretransmission is a sub-sequence determined based on the first polarchannel sequence.

It should be understood that data transmissions may require a samequantity of information bits or different quantities of informationbits. For example, when m=2, a quantity of information bits that need tobe transmitted during a second data transmission is K₂; when m=3, aquantity of information bits that need to be transmitted during a thirddata transmission is K₃, . . . , where K₂ and K₃ may be equal or notequal. In an implementation, K₃ is less than K₂, in other words, for them^(th) data transmission, K_(m) is less than K_(m)−₁. However, thisembodiment of this application is not limited thereto.

It should be further understood that, before an initial datatransmission is performed, the transmit device may obtain thereliability of each of the N polar channels, and when performing asubsequent retransmission, the transmit device selects at least onepolar channel with highest reliability based on the previously obtainedreliability of each polar channel. Specifically, the reliability of thepolar channels may be calculated through density evolution (DE) orGaussian approximation (GA).

Therefore, according to the polar code retransmission method in thisembodiment of this application, the same polar channel sequence is usedduring each data transmission, and the determined K_(m) information bitsare directly mapped to the K_(m) polar channels with highest reliabilityin the polar channel sequence for transmission, without recalculatingthe reliability of the polar channels before each retransmission. Thiscan reduce retransmission complexity and improve transmissionperformance, thereby improving user experience.

That the transmit device needs to perform the m^(th) data transmissionmeans that after the (m−1)^(th) data transmission is performed, thetransmit device needs to perform the m^(th) data transmission after areceive device fails to decode data transmitted during the (m−1)^(th)transmission. Specifically, the transmit device may acknowledge,according to received negative acknowledgement (NACK) information, thatthe receive device fails to decode the data.

It should be understood that m is not equal to 1, and the foregoingembodiment represents each retransmission process. During an initialtransmission, if the transmit device is user equipment, the userequipment may determine information such as a code rate and a quantityof information bits that need to be transmitted during the transmissionby receiving scheduling information of a base station, for example, byreceiving indication information sent by the base station. Theindication information may include a modulation and coding scheme (MCS)and a quantity of resource blocks (RBs). The transmit device determinesthe code rate, a quantity of encoded bits, and the quantity ofinformation bits that need to be transmitted during the initialtransmission based on the indication information. In another casewithout scheduling, the transmit device obtains the foregoing codingparameter based on information such as an available transmissionresource, an agreed code rate, and a modulation order.

In an optional embodiment, the reliability of each polar channel is apolarization weight of the polar channel.

Specifically, the polarization weight is a broad concept, and is notlimited to a single construction method. For different polar codeconstruction manners, different methods are used for calculating apolarization weight. This is not limited in this embodiment of thisapplication.

In a specific implementation, for a polar code with a code length of 2raised to the power of n, that is, N=2^(n), N to-be-encoded bits includeinformation bits and frozen bits. First, it is determined, based on thecode length N, that there are N polar channels in total with channelsequence numbers 0 to N−1. The polar channel sequence numbers are usedas parameters, to perform operations sequentially, and calculate apolarization weight W of each of the N polar channels. All the polarchannels are sorted in descending order of the polarization weights, thefirst K_(m) polar channels are selected, and sequence numbers of thefirst K_(m) polar channels are used as a location set for placing theK_(m) information bits (to-be-encoded bits). After the K_(m) informationbits are placed in the previously selected location set, bits on otherlocations are set as frozen bits, to obtain a complete to-be-encoded bitsequence with a length of N. Finally, an encoding process of theto-be-encoded bit sequence is completed by using an encoding matrixG_(N) of the polar code.

Specifically, the first polarization weight vector is obtained bycalculating the polarization weights W_(i) of the N polar channelsaccording to the following formula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

In an optional embodiment, the first polar channel sequence is generatedby sorting the N polar channels based on the reliability of each of theN polar channels.

Specifically, after obtaining the reliability of each of the N polarchannels, the transmit device may sort the N polar channels based on thereliability of each polar channel. The sorting may be performed inascending order or in descending order of reliability. This is notlimited in this embodiment of this application. After rankings of thereliability of the N polar channels are determined, the determinedinformation bits may be directly mapped to polar channels with highestrankings for transmission during each retransmission. In this way, thetransmit device does not need to determine a reliability value of eachof the N polar channels during each transmission, but only needs toobtain the first polar channel sequence obtained after the N polarchannels are sorted based on reliability values. This reduces complexityand improves coding efficiency.

In an optional embodiment, m is 2, and the K_(m) information bits areinformation bits that occupy K_(m) polar channels with lowestreliability in the first polar channel sequence during the first datatransmission.

Specifically, during a retransmission, the transmit device may selectinformation bits transmitted on polar channels with lowest reliabilityduring the first data transmission, and select K_(m) information bitsthat are corresponding to the polar channels with lowest reliability toperform the retransmission. In this way, a decoding success rate of thereceive device can be increased, and a quantity of retransmissions ofthe transmit device can be reduced.

In an optional embodiment, a code rate of the first data transmission isR, and a code rate of the m^(th) data transmission is

$\frac{R}{m},$where R is greater than 0 and less than 1.

The determining K_(m) information bits based on locations, ofinformation bits that need to be transmitted during first m−1 datatransmissions, in the first polar channel sequence includes:

determining K_(m-1) polar channels, corresponding to information bitsthat need to be transmitted during an (m−1)^(th) data transmission, inthe first polar channel sequence, where K_(m-1) is less than N andgreater than K_(m);

determining

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels with lowest reliability from the K_(m-1) polar m−1channels; and

determining the K_(m) information bits from information bits on the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions.

Specifically, before performing the m^(th) data transmission, thetransmit device may first determine the information bits used during the(m−1)^(th) data transmission, determine the polar channels occupied bythese information bits in the first polar channel sequence during the(m−1)^(th) data transmission, determine the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels with lowest reliability from these polar channels, andthen select the K_(m) information bits from information bits mapped tothe

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions, toperform the m^(th) data transmission.

For example, if the transmit device is to perform a third datatransmission, and a quantity of information bits that need to betransmitted during a first transmission is 12, according to a regularityof a code rate, a quantity of information bits that need to betransmitted during the third data transmission is 4, and iscorresponding to four polar channels with highest reliability. Thetransmit device may first select six information bits that need to betransmitted during a second data transmission, then determine six polarchannels corresponding to the six information bits, determine two polarchannels with lowest reliability from the six polar channels, and thenuse two information bits transmitted on the two polar channels duringthe first data transmission and two information bits transmitted on thetwo polar channels during the second data transmission as fourinformation bits that need to be transmitted during the third datatransmission.

It should be understood that, when K_(m) is indivisible by m−1,

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels first need to be determined; then,

$\lceil \frac{K_{m}}{m - 1} \rceil \times ( {m - 1} )$information bits mapped to the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions aredetermined, where

$\lceil \frac{K_{m}}{m - 1} \rceil \times ( {m - 1} )$is greater than K_(m); and finally, K_(m) information bits are selectedfrom the

$\lceil \frac{K_{m}}{m - 1} \rceil \times ( {m - 1} )$information bits as information bits, for the m^(th) data transmission,mapped to the K_(m) polar channels. Optionally, an information bit on apolar channel with low reliability may be selected based on locations,occupied by the

$\lceil \frac{K_{m}}{m - 1} \rceil \times ( {m - 1} )$information bits, in the first polar channel sequence during a previousdata transmission. This is not limited in this embodiment of thisapplication.

Therefore, information bits corresponding to most unreliable polarchannels during all previous data transmissions are comprehensivelyconsidered, and the information bits are mapped to polar channels withhighest reliability for retransmission, so as to enhance reliability ofthese most unreliable information bits, and increase a decoding successrate.

It should be understood that rankings of the K_(m) information bits onthe K_(m) polar channels with highest reliability in the first polarchannel sequence are not unique, and may be rankings of the K_(m)information bits used during the first transmission, or may be any otherrankings. This is not limited in this embodiment of this application.

In an optional embodiment, the mapping the K_(m) information bits to theK_(m) polar channels for transmission includes:

sorting the K_(m) information bits in descending order of reliability ofthe polar channels corresponding to the K_(m) information bits that needto be transmitted during the first data transmission; and

mapping, for transmission, the sorted K_(m) information bits to theK_(m) polar channels ranked in descending order of reliability.

Specifically, during each retransmission, the K_(m) information bits maybe mapped, in descending order of the reliability of the polar channelsoccupied by the K_(m) information bits during the first datatransmission, to the K_(m) polar channels ranked in descending order ofreliability.

Specifically, FIG. 3 is a schematic flowchart of another polar coderetransmission method according to an embodiment of this application. Asshown in FIG. 3, a first data transmission, a second data transmission,a third data transmission, and a fourth data transmission are includedfrom top to bottom.

Before the first data transmission, the transmit device may separatelycalculate reliability of 16 polar channels, and sort the 16 polarchannels from left to right in descending order of reliability.

During the first data transmission, the transmit device may determine 12information bits based on a code rate R of the first data transmission,add sequence numbers corresponding to 12 polar channels (12 polarchannels counting from the left) that have highest reliability rankingsinto a set A₁, and respectively transmit, on the 12 polar channelsrepresented by the set A₁, the 12 information bits: u₁, u₂, . . . , andu₁₂.

During the second data transmission, the transmit device may add, basedon a code rate R/2 of the second data transmission, sequence numberscorresponding to six polar channels that have highest reliabilityrankings into a set A₂, and further determine information bits mapped toA₁\A₂={a_(i)|a_(i)∈A₁,a_(i)∉A₂} channels during the first datatransmission, that is, u₇, u₈, u₉, u₁₀, u₁₁, and u₁₂. The informationbits u₇, u₈, u₉, u₁₀, u₁₁, and u₁₂ are separately mapped to the polarchannels represented by the set A₂ for transmission.

The determined code rate of the second data transmission is R/2 becausewhen there is no feedback information from the receive device, it isexpected that a code rate of each transmission is obtained through evendivision. For example, when the code rate of the initial transmission isR, half of information bits are used for retransmission in the firstretransmission, and after one retransmission, the code rates of theinitial transmission and the first retransmission are R/2. When channelquality of the initial transmission and channel quality of the firstretransmission are the same, this policy of evenly dividing a code ratecan ensure that decoding success rates for the two transmissions are thesame, preventing a case in which decoding fails due to an excessivelyhigh code rate of one transmission. Likewise, a code rate of eachsubsequent data transmission may be determined.

Likewise, during the third data transmission, the transmit device mayadd, based on a code rate R/3 of the third data transmission, sequencenumbers corresponding to four polar channels that have highestreliability rankings into a set A₃, further determine information bitsu₅ and u₆ mapped to A₂\A₃={a_(i)|a_(i)∈A₂,a_(i)∉A₃} channels during thefirst data transmission and information bits u₁₁ and u₁₂ mapped toA₂\A₃={a_(i)|a_(i)∈A₂,a_(i)∉A₃} channels during the second datatransmission, and finally separately map an information bit sequence u₅,u₆, u₁₁, u₁₂ to the polar channels represented by the set A₃ fortransmission.

During the fourth data transmission, the transmit device may add, basedon a code rate R/4 of the fourth data transmission, sequence numberscorresponding to three polar channels that have highest reliabilityrankings into a set A₄, further determine an information bit u₄ mappedto an A₃\A₄={a_(i)|a_(i)∈A₃,a_(i)∉A₄} channel during the first datatransmission, an information bit u₁₀ mapped to anA₃\A₄={a_(i)|a_(i)∈A₃,a_(i)∉A₄} channel during the second datatransmission, and an information bit u₁₂ mapped to anA₃\A₄={a_(i)|a_(i)∈A₃,a_(i)∉A₄} channel during the third datatransmission, and finally separately map an information bit sequence u₄,u₁₀, u₁₂ to the polar channels represented by the set A₄ fortransmission.

During each retransmission, information bits are mapped to the firstpolar channel sequence strictly in an order of information bits thatneed to be transmitted during the first data transmission. FIG. 3 isused as an example. If the order of the information bits that need to betransmitted during the first transmission is u₁, u₂, . . . , and u₁₂, anorder of information bits that need to be transmitted during the secondtransmission is u₇, u₈, u₉, u₁₀, u₁₁, and u₁₂, an order of informationbits that need to be transmitted during the third transmission is u₅,u₆, u₁₁, and u₁₂, and an order of information bits that need to betransmitted during the fourth transmission is u₄, u₁₀, and u₁₂. However,it should be understood that this is not limited in this embodiment ofthis application, and a subsequent retransmission may be performed inany other order. For example, the order of the information bits thatneed to be transmitted during the second transmission is u₁₂, u₁₁, . . ., and u₁, the order of the information bits that need to be transmittedduring the third transmission is u₁₁, u₁₂, u₉, and u₆, and the order ofthe information bits that need to be transmitted during the fourthtransmission is u₄, u₁₀, and u₁₂. This is not limited in this embodimentof this application.

It should be understood that a coding parameter for each datatransmission may be fixed or may be adaptively changed. This is notlimited in this embodiment of this application. Specifically, thetransmit device may determine, in a plurality of manners, the codingparameter for each data transmission.

In an optional embodiment, the determining the coding parameter for them^(th) data transmission includes:

determining a preset coding parameter as the coding parameter for them^(th) data transmission.

Specifically, the preset coding parameter may be agreed on by thetransmit device and the receive device in advance, or may be determinedbased on feedback information sent by the receive device. In short, thepreset coding parameter is fixed or is determined according to aspecific rule. In a specific implementation, if the code rate of theinitial transmission is R, and the receive device and the transmitdevice agree on a rule of a code rate of each retransmission in advance,the code rate of the second transmission is

$\frac{R}{2},$the code rate of the third transmission is

$\frac{R}{3},$. . . , and a code rate of the m^(th) transmission is

$\frac{R}{m}.$

In an optional embodiment, the determining the coding parameter for them^(th) data transmission includes:

receiving feedback information sent by the receive device for the(m−1)^(th) data transmission; and

determining the coding parameter for the m^(th) data transmission basedon the feedback information for the (m−1)^(th) data transmission.

In other words, during a data retransmission, a code length, aretransmission code rate, or a quantity of information bits can bedetermined based on quality of a channel for a previous datatransmission. The feedback information may include channel stateinformation (CSI), a signal to interference plus noise ratio (SINR), ora channel quality indicator (CQI) in Long Term Evolution (LTE); or mayinclude a code rate directly sent by the receive device; or may includea modulation and coding scheme (MCS), a transmission resource size, orthe like. The coding parameter includes one or more parameters of a codelength, a code rate, and a quantity of information bits.

It should be understood that a quantity of encoded bits is a codelength. The two concepts are interchangeable in the embodiment of thisapplication. It should be further understood that a quantity ofinformation bits may be determined by using a code length and a coderate, or a code rate may be determined by using a code length and aquantity of information bits. In other words, a third parameter may bededuced by using only two of the three parameters. In addition, otherinformation that can be used to instruct the transmit device todetermine the coding parameter shall fall within the protection scope ofthe embodiments of this application.

Specifically, the feedback information may include a CQI or an SINR. TheCQI is used as an example. There is a mapping table between a CQI and acode rate, so that the code rate may be determined by using the CQI. Inother words, an actually allowed code rate on a channel during aprevious transmission can be determined from the received feedbackinformation, and when a transmission resource is unchanged, a code rateof a current retransmission can be determined based on a code rate thatcan be actually provided on a channel during the previous transmission.Further, because the transmission resource is unchanged, a code lengthis unchanged. Therefore, a quantity of information bits that areretransmitted this time may be determined by using the code rate and thecode length.

Therefore, in this embodiment of this application, the transmit devicecan adjust, by using the feedback information sent by the receivedevice, a coding parameter such as a code rate, a code length, or aquantity of information bits, so as to adaptively change a code rateduring a retransmission.

FIG. 4 is a schematic diagram of an encoder according to an embodimentof this application. As shown in FIG. 4, M is a maximum quantity oftransmissions (including an initial transmission). Specifically, bitsthat are encoded again each time include some information bits duringall previous data transmissions, and information bits selected each timeare information bits that are restructured based on a currentretransmission code rate and that are corresponding to polar channelswith lower reliability during all the previous data transmissions. Aspecific process of selecting an information bit is the same as that inthe method described in the foregoing embodiment. Details are notdescribed herein again.

FIG. 5 is a schematic flowchart of a polar code retransmission method300 according to an embodiment of this application. The method 300 maybe applied to the wireless communications system 100 in FIG. 1. However,this embodiment of this application is not limited thereto. In addition,the method 300 may be performed by a network device, or may be userequipment. As shown in FIG. 3, the method 300 includes the followingsteps:

S310. Determine a first polar channel sequence including N polarchannels and reliability of each of the N polar channels.

S320. Determine, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate.

S330. Determine K_(m) polar channels with highest reliability in thefirst polar channel sequence.

S340. Decode, on the K_(m) polar channels, data transmitted during them^(th) data transmission.

Herein, m, K_(m), and N are positive integers, m is greater than 1, andK_(m) is less than N.

Therefore, according to the polar code retransmission method in thisembodiment of this application, during each data transmission, K_(m)polar channels are directly determined by using the same polar channelsequence, and received data is directly decoded on the K_(m) polarchannels, without recalculating reliability of the polar channels beforeeach reception of data retransmitted by a transmit device. This canreduce decoding complexity and improve transmission performance, therebyimproving user experience.

In an optional embodiment, the first polar channel sequence is generatedby sorting the N polar channels based on the reliability of each of theN polar channels.

In an optional embodiment, the method further includes:

sending feedback information to a transmit device, so that the transmitdevice determines the coding parameter for the m^(th) data transmissionbased on the feedback information.

In an optional embodiment, the reliability of each polar channel is apolarization weight of the polar channel.

In an optional embodiment, before the determining a first polar channelsequence including N polar channels and reliability of each of the Npolar channels, the method further includes:

calculating the polarization weight of each of the N polar channels.

In an optional embodiment, the calculating the polarization weight ofeach of the N polar channels includes:

obtaining the first polarization weight vector by calculating thepolarization weights W_(i) of the N polar channels according to thefollowing formula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

It should be understood that sequence numbers of the foregoing processesdo not mean particular execution sequences. The execution sequences ofthe processes should be determined based on functions and internal logicof the processes, and should not be construed as any limitation on theimplementation processes of the embodiments of this application.

The foregoing describes in detail the polar code retransmission methodaccording to the embodiments of this application with reference to FIG.1 to FIG. 5. The following describes in detail a polar coderetransmission apparatus according to embodiments of this applicationwith reference to FIG. 6 to FIG. 9.

FIG. 6 is a schematic block diagram of a polar code retransmissionapparatus 400 according to an embodiment of this application. Theapparatus 400 includes:

a determining unit 410, configured to: determine a first polar channelsequence including N polar channels and reliability of each of the Npolar channels;

determine, based on a coding parameter for an m^(th) data transmission,a quantity K_(m) of information bits that need to be transmitted duringthe m^(th) data transmission, where the coding parameter includes atleast one of the quantity of information bits and a code rate;

determine K_(m) polar channels with highest reliability in the firstpolar channel sequence; and

determine K_(m) information bits based on locations, of information bitsthat need to be transmitted during first m−1 data transmissions, in thefirst polar channel sequence; and

a sending unit 420, configured to map the K_(m) information bits to theK_(m) polar channels for transmission, where

m, K_(m), and N are positive integers, m is greater than 1, and K_(m) isless than N.

Therefore, according to the polar code retransmission apparatus in thisembodiment of this application, the same polar channel sequence is usedduring each data transmission, and the determined K_(m) information bitsare directly mapped to the K_(m) polar channels with highest reliabilityin the polar channel sequence for transmission, without recalculatingthe reliability of the polar channels before each retransmission. Thiscan reduce retransmission complexity and improve transmissionperformance, thereby improving user experience.

Optionally, m is 2, and the K_(m) information bits are information bitsthat occupy K_(m) polar channels with lowest reliability in the firstpolar channel sequence during a first data transmission.

Optionally, a code rate of the first data transmission is R, and a coderate of the m^(th) data transmission is

$\frac{R}{m},$where R is greater than 0 and less than 1. The determining unit isspecifically configured to: determine K_(m-1) polar channels,corresponding to information bits that need to be transmitted during an(m−1)^(th) data transmission, in the first polar channel sequence, whereK_(m-1) is less than N and greater than K_(m); determine

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels with lowest reliability from the K_(m-1) polar channels;and determine the K_(m) information bits from information bits on the

$\lceil \frac{K_{m}}{m - 1} \rceil$polar channels during each of the first m−1 data transmissions.

Optionally, the apparatus further includes: a sorting unit, configuredto sort the K_(m) information bits in descending order of reliability ofthe polar channels corresponding to the K_(m) information bits that needto be transmitted during the first data transmission. The sending unit420 is specifically configured to map, for transmission, the sortedK_(m) information bits to the K_(m) polar channels ranked in descendingorder of reliability.

Optionally, the determining unit 410 is further configured to: beforedetermining, based on the coding parameter for the m^(th) datatransmission, the quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, determine the codingparameter for the m^(th) data transmission.

Optionally, the determining unit 410 is specifically configured todetermine a preset coding parameter as the coding parameter for them^(th) data transmission.

Optionally, the apparatus further includes: a receiving unit, configuredto receive feedback information sent by a receive device for the(m−1)^(th) data transmission. The determining unit 410 is specificallyconfigured to determine the coding parameter for the m^(th) datatransmission based on the feedback information for the (m−1)^(th) datatransmission.

Optionally, the first polar channel sequence is generated by sorting theN polar channels based on the reliability of each of the N polarchannels.

Optionally, the reliability of each polar channel is a polarizationweight of the polar channel.

Optionally, the apparatus further includes: a calculation unit,configured to: before the first polar channel sequence including the Npolar channels and the reliability of each of the N polar channels aredetermined, calculate the polarization weight of each of the N polarchannels.

Optionally, the calculation unit is specifically configured to obtainthe first polarization weight vector by calculating the polarizationweights W_(i) of the N polar channels according to the followingformula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

It should be understood that the apparatus 400 herein is embodied in aform of functional units. The term “unit” herein may be anapplication-specific integrated circuit (application-specific integratedcircuit, ASIC), an electronic circuit, a processor (for example, ashared processor, a dedicated processor, or a group processor)configured to execute one or more software or firmware programs and amemory, a combinational logic circuit, and another appropriate componentthat supports the described functions. In an optional example, a personskilled in the art may understand that the apparatus 400 may bespecifically the transmit device in the foregoing embodiments, and theapparatus 400 may be configured to perform procedures and steps that arecorresponding to the transmit device in the foregoing methodembodiments. To avoid repetition, details are not described hereinagain.

FIG. 7 is a schematic block diagram of a polar code retransmissionapparatus 500 according to an embodiment of this application. Theapparatus 500 includes:

a determining unit 510, configured to: determine a first polar channelsequence including N polar channels and reliability of each of the Npolar channels;

determine, based on a coding parameter for an m^(th) data transmission,a quantity K_(m) of information bits that need to be transmitted duringthe m^(th) data transmission, where the coding parameter includes atleast one of the quantity of information bits and a code rate; and

determine K_(m) polar channels with highest reliability in the firstpolar channel sequence; and

a decoding unit 520, configured to decode, on the K_(m) polar channels,data transmitted during the m^(th) data transmission, where

m, K_(m), and N are positive integers, m is greater than 1, and K_(m) isless than N.

Therefore, according to the polar code retransmission apparatus in thisembodiment of this application, during each data transmission, K_(m)polar channels are directly determined by using the same polar channelsequence, and received data is directly decoded on the K_(m) polarchannels, without recalculating reliability of the polar channels beforeeach reception of data retransmitted by a transmit device. This canreduce decoding complexity and improve transmission performance, therebyimproving user experience.

Optionally, the first polar channel sequence is generated by sorting theN polar channels based on the reliability of each of the N polarchannels.

Optionally, the apparatus further includes:

a sending unit, configured to send feedback information to a transmitdevice, so that the transmit device determines the coding parameter forthe m^(th) data transmission based on the feedback information.

Optionally, the reliability of each polar channel is a polarizationweight of the polar channel.

Optionally, the apparatus further includes: a calculation unit,configured to: before the first polar channel sequence including the Npolar channels and the reliability of each of the N polar channels aredetermined, calculate the polarization weight of each of the N polarchannels.

Optionally, the calculation unit is specifically configured to obtainthe first polarization weight vector by calculating the polarizationweights W_(i) of the N polar channels according to the followingformula:

${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$

where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.

It should be understood that the apparatus 500 herein is embodied in aform of functional units. The term “unit” herein may be anapplication-specific integrated circuit (application-specific integratedcircuit, ASIC), an electronic circuit, a processor (for example, ashared processor, a dedicated processor, or a group processor)configured to execute one or more software or firmware programs and amemory, a combinational logic circuit, and another appropriate componentthat supports the described functions. In an optional example, a personskilled in the art may understand that the apparatus 500 may bespecifically the receive device in the foregoing embodiments, and theapparatus 500 may be configured to perform procedures and steps that arecorresponding to the receive device in the foregoing method embodiments.To avoid repetition, details are not described herein again.

FIG. 8 shows a polar code retransmission apparatus 600 according to anembodiment of this application. The apparatus 600 includes a processor610, a transceiver 620, a memory 630, and a bus system 640. Theprocessor 610, the transceiver 620, and the memory 630 are connected byusing the bus system 640, the memory 630 is configured to store aninstruction, and the processor 610 is configured to execute theinstruction stored in the memory 630, to control the transceiver 620 tosend a signal and receive a signal.

The processor 610 is configured to: determine a first polar channelsequence including N polar channels and reliability of each of the Npolar channels; determine, based on a coding parameter for an m^(th)data transmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate; determine K_(m) polar channels with highest reliability inthe first polar channel sequence; determine K_(m) information bits basedon locations, of information bits that need to be transmitted duringfirst m−1 data transmissions, in the first polar channel sequence; andinstruct the transceiver 620 to map the K_(m) information bits to theK_(m) polar channels for transmission, where m, K_(m), and N arepositive integers, m is greater than 1, and K_(m) is less than N.

It should be understood that the apparatus 600 may be specifically thetransmit device in the foregoing embodiments, and may be configured toperform steps and/or procedures that are corresponding to the transmitdevice in the foregoing method embodiments. Optionally, the memory 630may include a read-only memory and a random access memory, and providean instruction and data for the processor. A part of the memory mayfurther include a non-volatile random access memory. For example, thememory may further store information about a device type. The processor610 may be configured to execute the instruction stored in the memory.When the processor executes the instruction stored in the memory, theprocessor is configured to perform the steps and/or the procedures thatare corresponding to the transmit device in the foregoing methodembodiments.

FIG. 9 shows a polar code retransmission apparatus 700 according to anembodiment of this application. The apparatus 700 includes a processor710, a transceiver 720, a memory 730, and a bus system 740. Theprocessor 710, the transceiver 720, and the memory 730 are connected byusing the bus system 740, the memory 730 is configured to store aninstruction, and the processor 710 is configured to execute theinstruction stored in the memory 730, to control the transceiver 720 tosend a signal and receive a signal.

The processor 710 is configured to: determine a first polar channelsequence including N polar channels and reliability of each of the Npolar channels; determine, based on a coding parameter for an m^(th)data transmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, where the codingparameter includes at least one of the quantity of information bits anda code rate; determine K_(m) polar channels with highest reliability inthe first polar channel sequence; and decode, on the K_(m) polarchannels, data transmitted during the m^(th) data transmission, where m,K_(m), and N are positive integers, m is greater than 1, and K_(m) isless than N.

It should be understood that the apparatus 700 may be specifically thereceive device in the foregoing embodiments, and may be configured toperform steps and/or procedures that are corresponding to the receivedevice in the foregoing method embodiments. Optionally, the memory 730may include a read-only memory and a random access memory, and providean instruction and data for the processor. A part of the memory mayfurther include a non-volatile random access memory. For example, thememory may further store information about a device type. The processor710 may be configured to execute the instruction stored in the memory.When the processor executes the instruction stored in the memory, theprocessor is configured to perform the steps and/or the procedures thatare corresponding to the receive device in the foregoing methodembodiments.

It should be understood that in the embodiments of this application, theprocessor may be a central processing unit (CPU), or the processor maybe another general purpose processor, a digital signal processor (DSP),an application-specific integrated circuit (ASIC), a field programmablegate array (FPGA) or another programmable logic device, a discrete gateor transistor logic device, a discrete hardware component, or the like.The general purpose processor may be a microprocessor, or the processormay be any conventional processor or the like.

In an implementation process, each step of the foregoing method may becompleted by using an integrated logical circuit of hardware in theprocessor or an instruction in a form of software. The steps of themethods disclosed with reference to the embodiments of this applicationmay be directly performed and completed by a hardware processor, or maybe performed and completed by using a combination of hardware andsoftware modules in the processor. A software module may be located in amature storage medium in the art, such as a random access memory, aflash memory, a read-only memory, a programmable read-only memory, anelectrically erasable programmable memory, a register, or the like. Thestorage medium is located in the memory, and the processor executesinstructions in the memory and completes the steps in the foregoingmethods in combination with hardware of the processor. To avoidrepetition, details are not described herein again.

FIG. 10 and FIG. 11 each are a schematic diagram of transmissionperformance of a polar code retransmission method according to anembodiment of this application.

In the retransmission method in the embodiments of this application, apolar channel sequence needs to be constructed only once. However, in amethod used for comparison, for each HARQ retransmission, reliability ofa polar channel needs to be calculated and a polar channel sequenceneeds to be reconstructed. The following gives specific parameters forsimulation and comparison. The specific parameters are as follows: On anadditive white Gaussian noise (AWGN) channel, a given code length is8000, a code rate is ⅚ and 8/9, and a modulation order is 6.

FIG. 10 and FIG. 11 each show analog curves of four transmissions. Itcan be seen from the analog curves that performance of the technicalsolutions proposed in the embodiments of this application is close toperformance of the prior art, and a performance difference falls withina range of 0.1 dB to 0.2 dB on the AWGN channel. However, the solutionsproposed in the embodiments of this application are of low complexity,are easy to operate, and can improve transmission performance.

It should be understood that “one embodiment” or “an embodiment”mentioned in the whole specification means that particular features,structures, or characteristics related to the embodiment are included inat least one embodiment of this application. Therefore, “in oneembodiment” or “in an embodiment” appearing throughout the specificationdoes not refer to a same embodiment. Moreover, the particularcharacteristic, structure or property may be combined in one or moreembodiments in any proper manner. It should be understood that sequencenumbers of the foregoing processes do not mean particular executionsequences in various embodiments of this application. The executionsequences of the processes should be determined based on functions andinternal logic of the processes, and should not be construed as anylimitation on the implementation processes of the embodiments of thisapplication.

In addition, the terms “system” and “network” may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases: Only Aexists, both A and B exist, and only B exists. In addition, thecharacter “/” in this specification usually indicates an “or”relationship between the associated objects.

It should be understood that in the embodiments of this application, “Bcorresponding to A” indicates that B is associated with A, and B may bedetermined based on A. However, it should be further understood thatdetermining B based on A does not mean that B is determined based on Aonly; that is, B may also be determined based on A and/or otherinformation.

A person of ordinary skill in the art may be aware that, the units andsteps in the examples described with reference to the embodimentsdisclosed herein may be implemented by electronic hardware, computersoftware, or a combination thereof. To clearly describe theinterchangeability between the hardware and the software, the foregoinghas generally described compositions and steps of each example based onfunctions. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments, and detailsare not described herein.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented through some interfaces, indirect couplings or communicationconnections between the apparatuses or units, or electrical connections,mechanical connections, or connections in other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualneeds to achieve the objectives of the solutions of the embodiments ofthis application.

In addition, functional units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit. Theintegrated unit may be implemented in a form of hardware, or may beimplemented in a form of a software functional unit.

With descriptions of the foregoing implementations, a person skilled inthe art may clearly understand that this application may be implementedby hardware, firmware or a combination thereof. When this application isimplemented by software, the foregoing functions may be stored in acomputer-readable medium or transmitted as one or more instructions orcode in the computer-readable medium. The computer-readable mediumincludes a computer storage medium and a communications medium, wherethe communications medium includes any medium that enables a computerprogram to be transmitted from one place to another. The storage mediummay be any available medium accessible to a computer. For example butnot for limitation, the computer-readable medium may include a RAM, aROM, an EEPROM, a CD-ROM, or another optical disc storage or diskstorage medium, or another magnetic storage device, or any other mediumthat can carry or store expected program code in a form of aninstruction or a data structure and can be accessed by a computer. Inaddition, any connection may be appropriately defined as acomputer-readable medium. For example, if software is transmitted from awebsite, a server, or another remote source by using a coaxial cable, anoptical fiber/cable, a twisted pair, a digital subscriber line (DSL), orwireless technologies such as infrared ray, radio, and microwave, thecoaxial cable, optical fiber/cable, twisted pair, DSL, or wirelesstechnologies such as infrared ray, radio, and microwave are included ina definition of the medium. As used in this application, disks (Disk)and discs (disc) include a compact disc (CD), a laser disc, an opticaldisc, a digital versatile disc (DVD), a floppy disk, and a Blu-ray disc.The disk usually copies data by a magnetic means, and the disc opticallycopies data by a laser means. The foregoing combination should also beincluded in the protection scope of the computer-readable medium.

In conclusion, the foregoing descriptions are merely examples ofembodiments of the technical solutions of this application, but are notintended to limit the protection scope of this application. Anymodification, equivalent replacement, or improvement made withoutdeparting from the principle of this application shall fall within theprotection scope of this application.

What is claimed is:
 1. A polar code retransmission method, the methodcomprising: determining a first polar channel sequence comprising Npolar channels and reliability of each of the N polar channels;determining, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, wherein the codingparameter comprises at least one of the quantity of information bits anda code rate; determining K_(m) polar channels with highest reliabilityin a first polar channel sequence; determining K_(m) information bitsbased on locations, of information bits that need to be transmittedduring first m−1 data transmissions, in the first polar channelsequence; and mapping the K_(m) information bits to the K_(m) polarchannels for transmission; wherein m, K_(m), and N are positiveintegers, m is greater than 1, and K_(m) is less than N.
 2. The methodaccording to claim 1, wherein m is 2, and the K_(m) information bits areinformation bits that occupy K_(m) polar channels with lowestreliability in the first polar channel sequence during a first datatransmission.
 3. The method according to claim 1, wherein a code rate ofthe first data transmission is R, and a code rate of the m^(th) datatransmission is $\frac{R}{m},$ wherein R is greater than 0 and less than1; and determining K_(m) information bits based on locations, ofinformation bits that need to be transmitted during first m−1 datatransmissions, in the first polar channel sequence comprises:determining K_(m-1) polar channels, corresponding to information bitsthat need to be transmitted during an (m−1)^(th) data transmission, inthe first polar channel sequence, wherein K_(m-1) is less than N andgreater than K_(m); determining$\lceil \frac{K_{m}}{m - 1} \rceil$  polar channels withlowest reliability from the K_(m-1) polar channels; and determining theK_(m) information bits from information bits on the$\lceil \frac{K_{m}}{m - 1} \rceil$  polar channels duringeach of the first m−1 data transmissions.
 4. The method according toclaim 1, wherein mapping the K_(m) information bits to the K_(m) polarchannels for transmission comprises: sorting the K_(m) information bitsin descending order of reliability of the polar channels correspondingto the K_(m) information bits that need to be transmitted during thefirst data transmission; and mapping, for transmission, the sorted K_(m)information bits to the K_(m) polar channels ranked in descending orderof reliability.
 5. The method according to claim 1, wherein beforedetermining, based on a coding parameter for an m^(th) datatransmission, a quantity K_(m) of information bits that need to betransmitted during the m^(th) data transmission, the method furthercomprises: determining the coding parameter for the m^(th) datatransmission.
 6. The method according to claim 5, wherein determiningthe coding parameter for the m^(th) data transmission comprises:determining a preset coding parameter as the coding parameter for them^(th) data transmission.
 7. The method according to claim 5, whereindetermining the coding parameter for the m^(th) data transmissioncomprises: receiving feedback information sent by a receive device forthe (m−1)^(th) data transmission; and determining the coding parameterfor the m^(th) data transmission based on the feedback information forthe (m−1)^(th) data transmission.
 8. The method according to claim 1,wherein the first polar channel sequence is generated by sorting the Npolar channels based on the reliability of each of the N polar channels.9. A polar code retransmission method, the method comprising:determining a first polar channel sequence comprising N polar channelsand reliability of each of the N polar channels; determining, based on acoding parameter for an m^(th) data transmission, a quantity K_(m) ofinformation bits that need to be transmitted during the m^(th) datatransmission, wherein the coding parameter comprises at least one of thequantity of information bits and a code rate; determining K_(m) polarchannels with highest reliability in the first polar channel sequence;and decoding, on the K_(m) polar channels, data transmitted during them^(th) data transmission; wherein m, K_(m), and N are positive integers,m is greater than 1, and K_(m) is less than N.
 10. The method accordingto claim 9, wherein the first polar channel sequence is generated bysorting the N polar channels based on the reliability of each of the Npolar channels.
 11. The method according to claim 9, wherein the methodfurther comprises: sending feedback information to a transmit device fordetermining the coding parameter for the m^(th) data transmission basedon the feedback information.
 12. The method according to claim 9,wherein the reliability of each polar channel is a polarization weightof the polar channel.
 13. The method according to claim 12, whereinbefore determining a first polar channel sequence comprising of N polarchannels and reliability of each of the N polar channels, the methodfurther comprises: calculating the polarization weight of each of the Npolar channels.
 14. The method according to claim 13, whereincalculating the polarization weights of the N polar channels comprises:obtaining the first polarization weight vector by calculating thepolarization weights W_(i) of the N polar channels according to thefollowing formula:${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.
 15. A polar coderetransmission apparatus, comprising: a transceiver; a memory,configured to store one or more instructions; a processor, separatelycoupled to the memory and the transceiver, and configured to execute theone or more instructions stored in the memory to cause the apparatus to:determine a first polar channel sequence comprising of N polar channelsand reliability of each of the N polar channels; determine, based on acoding parameter for an m^(th) data transmission, a quantity K_(m) ofinformation bits that need to be transmitted during the m^(th) datatransmission, wherein the coding parameter comprises at least one of thequantity of information bits and a code rate; determine K_(m) polarchannels with highest reliability in the first polar channel sequence;and decode, on the K_(m) polar channels, data transmitted during them^(th) data transmission; wherein m, K_(m), and N are positive integers,m is greater than 1, and K_(m) is less than N.
 16. The apparatusaccording to claim 15, wherein the first polar channel sequence isgenerated by sorting the N polar channels based on the reliability ofeach of the N polar channels.
 17. The apparatus according to claim 15,wherein the transceiver is further configured to: send feedbackinformation to a transmit device for determining the coding parameterfor the m^(th) data transmission based on the feedback information. 18.The apparatus according to claim 15, wherein the reliability of eachpolar channel is a polarization weight of the polar channel.
 19. Theapparatus according to claim 18, wherein the processor is configured toexecute the one or more instructions to cause the apparatus to: beforethe first polar channel sequence comprising the N polar channels and thereliability of each of the N polar channels are determined, calculatethe polarization weight of each of the N polar channels.
 20. Theapparatus according to claim 19, wherein the processor is configured toexecute the one or more instructions to cause the apparatus to: obtain afirst polarization weight vector by calculating the polarization weightsW of the N polar channels according to the following formula:${W_{i} = {\sum\limits_{j = 0}^{n - 1}{B_{j}*( {2^{j} + \phi} )^{\alpha}}}},$where i

B_(n-1)B_(n-2) . . . B₀, i is a channel index, B_(n-1)B_(n-2) . . . B₀is a binary representation of i, B_(n-1) is a most significant bit, B₀is a least significant bit, B_(j)∈{0,1}, j∈{0, 1, . . . , n−1}, i∈{0, 1,. . . , n−1}, N=2^(n), ϕ and α are parameters preset based on a targetcode length of a first data transmission and a code rate of the firstdata transmission, and n is a positive integer.